Method for packaging a block consisting of a compressible material, a device for carrying out said method and a correspondingly packaged block

ABSTRACT

In a method and an apparatus for packaging a block consisting of compressible material, a material block is compressed by approaching two pressing units ( 120,122 ), the block being shifted in the compressed condition either against a spread film and wrapped by this film or, alternatively, the film is shifted against the material block and drawn over the material block. The ends of the film are weld together.

[0001] This invention relates to a method for packaging a block consisting of a compressible material according to the preamble of claim 1, a corresponding device for packaging the block according to the preamble of claim 5 and the block that is packaged by means of this method and device.

[0002] These types of methods and devices are used in particular for blocks of material which consist of an airlaid material and are intended for further processing to manufacture hygiene articles.

[0003] A block of material of this type is disclosed in e.g. DE 299 10 039 U1. This block of material consists of a plaited web of material which is divided into several adjacent strips and is perforated. The ends of the individual strips are sewn together in a special way to form a continuous strip.

[0004] After fabrication, the block of material is compressed to a certain degree and inserted into a plastic bag in this compressed state.

[0005] After the plastic bag has been glued shut manually, the pressure on the block of material is released, whereupon it expands so that it presses against every part of the inside wall of the plastic bag. In this state, the block of material has a relatively low transport volume and high stability.

[0006] The disadvantage is that the insertion of the compressed block of material into the plastic bag, the sealing of the plastic bag and the handling of both the empty and filled plastic bags are all done manually. This makes the production process slow and the block of the material is therefore expensive.

[0007] DE 196 40 953 A1 discloses a method for packaging compressible hygiene articles in which several identical hygiene articles are oriented parallel to each other and pushed as a block through a tapering inlet pipe into a continuous plastic hose.

[0008] Filled in this way, the plastic hose is then cut between every two adjacent blocks and welded. One disadvantage amongst others of this method is that the movement to insert the hygiene article into the plastic hose has to be transverse to the previous transport movement of the hygiene articles, which considerably enlarges the amount of space required for such a packaging machine, thereby making the machine more expensive. A further disadvantage is that only a limited length of plastic hose can be employed, which is therefore all used up within a short time. This means frequent interruptions to the otherwise continuous packaging process. Furthermore, a plastic sleeve of this type is relatively expensive. There is also a significant technical disadvantage to this method in that it requires a push-in force which subdivides at the tapering inlet pipe and pushes the hygiene article into the hose with the greater force component whilst at the same time ensuring the compression of the hygiene article with the smaller force component. Larger blocks of material cannot be sufficiently compressed. Simply increasing the overall push-in force, however, would damage the hygiene article.

[0009] The invention is therefore based on the task of developing a generic method of packaging a block consisting of a compressible material which allows the use of large compressing forces and a continuous work cycle.

[0010] A further task of the invention is to develop a corresponding device for carrying out the method, which is robust yet simple and cost-saving.

[0011] Another task of this invention is to create an accordingly packaged block.

[0012] The method-related task is solved by the features of claim 1. Variations of the method are described in sub-claims 2 to 7.

[0013] The device-related task is solved by the features of claim 8, with advantageous variations thereof in the following sub-claims 9 to 24.

[0014] The features of the block are described in claim 25.

[0015] The invention overcomes the quoted disadvantages of the state of the art.

[0016] The special advantage of the invention resides in the exceptionally rational construction of the device, which fits very well into the upstream production process. This is due primarily to the fact that the direction in which the block of material is packaged coincides with the previous direction of transport of the block of material. Furthermore, no expensive, difficult-to-handle film bags or film sleeves are used as generally disclosed elsewhere, but rather a simple and inexpensive film web. This film web can easily be erected crosswise to the direction of transport of the block of material. This means it is very simple to realise two types of embodiments in line with the type of existing pre-manufacturing plant, in that either the stretched film web is moved towards the stationary block of material, or the block of material is moved towards the stationary film web. It is also possible, of course, to move the block of material and the transverse film web towards each other at the same rate.

[0017] It is very advantageous to use a film web wound on a roll of film. This ensures a long and uninterrupted production process. In practice, a section of film web of the required wrapping length is cut out of the continuous stretched film web and the two ends of the stretched film web and the two ends of the cut-out portion of film web are welded together simultaneously.

[0018] As already mentioned briefly, the invention comprises two embodiments. In the first embodiment, the film web is pulled over the block of material and in the second embodiment, the block of material is pushed through a curtain formed by the film web.

[0019] The device for packaging a compressible block of material can be adapted in a modified form to the most varied of production equipment. This broadens the scope of use of this device.

[0020] The invention will now be described in more detail below with reference to one embodiment by way of example and the enclosed drawings in which:

[0021]FIG. 1 shows a side view of the device according to the invention, in the position in which the block of material is compressed;

[0022]FIG. 2 shows a side view of the device, in the position in which the block of material is transferred to a mobile packaging apparatus;

[0023]FIG. 3 shows a side view of the device, in the position in which the block of material is enveloped by a film web;

[0024]FIG. 4 shows the compression unit in a first position;

[0025]FIG. 5 shows the compression unit in a second position;

[0026]FIG. 6 shows the compression unit in a third position;

[0027]FIG. 7 shows the compression unit in a fourth position;

[0028]FIG. 8 shows a diagrammatic side view of a device according to the invention;

[0029]FIG. 9 shows a top plan view of FIG. 8.

[0030] According to FIG. 1, the device essentially comprises a compression apparatus 1 and a packaging apparatus 2 for a block of material 3 consisting of an airlaid material.

[0031] Compression apparatus 1 is positioned at the end of a transport chain which is not shown here, being indicated merely by a direction arrow. Compression apparatus 1 consists of a frame 4 with a frame base 5, several frame pillars 6 and a top frame plate 7.

[0032] Fixed to top frame plate 7 there is a hydraulic cylinder unit 8 with a cylinder 9 and a piston rod 10.

[0033] Between the pivot axis of piston rod 10 and base 5, there is a compression unit 11 which is shown in more detail in FIGS. 4 to 7 in various positions, and which is designed to receive the block of material 3.

[0034] For this purpose compression unit 11 consists of a bottom, fixed compression plate 12 and a top compression plate 13 which can be vertically displaced to a limited degree by means of piston rod 10. Disposed between the bottom compression plate 12 and top compression plate 13 in the direction of transport of the block of material 3, there are two bottom angled compression rails 14 and two top angled compression rails 15 whose two sets of arms are adapted to the position and size of the four body edges of the block of material 3 showing in the direction of transport.

[0035] The two bottom angled compression rails 14 and the two top angled compression rails 15 are contrived such that they are vertically displaceable in a certain manner in relation to each other and in relation to the bottom compression plate 12 and the top compression plate 13. Thus the two bottom angled compression rails 14 can be moved in relation to the bottom fixed compression plate 12 by a height which, when bottom angled compression rails 14 reach their top position, forms a bottom free area 16, as shown in FIGS. 6 and 7. Likewise, the two top angled compression rails 15 can be moved in relation to top compression plate 13 by a height which forms a maximum upper free area 17. Compression unit 11 is also equipped with a clamping device (not shown) which fixes the two bottom angled compression rails 14 in relation to the two top angled compression rails 15 so that the compressed block of material 3 can be lifted without any loss of pressure. This clamping device is preferably hydraulic.

[0036] The packaging apparatus 2 includes a film stretching unit 18, a film welding unit 19 and a movable unit 20 which are disposed in this sequence downstream of compression apparatus 1. The film stretching unit 18 consists of a bottom pivot bearing for a roll of film 21 and a top tensioning roller 22 for a film web 23 whose width coincides with the width of the block of material 3.

[0037] The tensioning roller 22 is pre-tensioned to such a degree that film web 23 can be pushed out from its vertical starting position under a horizontal load and, if such a load is removed, will revert to its vertical starting position. Between the roll of film 21 and tensioning roller 22, a bottom pair of rollers 24 is disposed below the block of material 3 and a top pair of rollers 25 is disposed above the block of material 3, both designed to guide and deflect film web 23 on both sides.

[0038] These two pairs of rollers 24, 25, the roll of film 21 and tensioning roller 22 are preferably mounted on frame 4 of compression apparatus 1.

[0039] Movable unit 20 essentially consists of a frame 26 and a movable slide 27. On the side facing compression apparatus 1, this movable slide 27 has a bottom remover gripper 28 and a top remover gripper 29 which are vertically distanced from each other to coincide with the height of the block of material 3. The top remover gripper 29 is also contrived to be vertically displaceable and is connected to a drive device (not shown). The length of the two remover grippers 28, 29 and the position and length of the displacement path of movable slide 27 are contrived so that, in one end position of the movable unit 20, the two remover grippers 28, 29 engage in compression unit 11 of compression apparatus 1 and grip hold of the block of material 3 over its entire depth, and in the other end position are completely removed from compression unit 11.

[0040] As shown in FIG. 7, the two remover grippers 28, 29 are made from a flat material and have cross-section dimensions which allow them to be inserted between the two adjacent angled compression rails 14, 15.

[0041] Both the bottom remover gripper 28 and the top remover gripper 29 are fitted on their free ends closest to film web 23 with a crosswise film push rod 30 which comes into contact with the full width of film web 23. These two film push rods 30 are fixed a certain distance below the bottom remover gripper 28 and above top remover gripper 29 to compensate for the material thickness of angled compression rails 14, 15.

[0042] Between film web 23 and the film push rods 30 in their starting position there is sufficient space in which to dispose film welding unit 19. This film welding unit 19 is fitted with two vertically displaceable welding beams 31 which grip the entire width of film web 23 and which, in their starting position, rest outside the scope of action of movable unit 20 and come into contact with each other in their working position. One of welding beams 31 is fitted with an additional separating wire which extends across the entire length of welding beam 31, running along the middle of welding beam 31.

[0043] This separating wire is disposed in such a plane to the heating surface of welding beam 31 so that film web 23 is welded first and then separated within the welded surface. Other welding technologies can also be used.

[0044] In the starting position according to FIG. 1, the block of material 3 is moved into the position shown, where it is deposited on the two bottom angled compression rails 14. By operating the hydraulic cylinder unit 8, the compression unit 11 is then activated, as a result of which the two top angled compression rails 15 move downwards and exert pressure on the block of material 3 until the block of material 3 is sufficiently compressed. This position is shown in FIG. 4. The clamping device (not shown) is then activated, which fixes the two bottom angled compression rails 14 and the two top angled compression rails 15 in relation to each other. The pressure is now taken off compression unit 11, which is moved apart in the upwards direction. Top compression plate 13 first lifts up from the two top angled compression rails 15 and forms the top free space 17 as shown in FIG. 5. As this movement proceeds, the top angled compression rails 15, the block of material 3 and the bottom angled compression rails 14 lift up as a whole from the bottom compression plate 12 and form the bottom free space 16 (FIG. 6).

[0045] As shown in FIG. 2, the movable slide 27 of movable unit 20 then moves into the opened compression unit 11. As this happens, the bottom remover gripper 28 with its film push rod 30 moves into the bottom free space 16 and the top remover gripper 29 with its film push rod 30 moves into the top free space 17 as shown in FIG. 7.

[0046] During this displacement, the two film push rods 30 come into contact with film web 23 and pull it with the help of the two pairs of rollers 24, 25, into the two free spaces 16 and 17. The top remover gripper 29 then moves downwards and holds the block of material 3 in place between both remover grippers 28, 29. The pressure is then taken off the clamping device for the bottom and top angled compression rails 14, 15, thereby releasing the block of material 3 so that the movable slide 27 on the movable unit 20 moves back into its starting position with the partially enveloped block of material 3 as shown in FIG. 3.

[0047] During this movement of the movable slide 27, the film web 23 is constantly held taut by the pre-tensioning of tensioning roller 22. After reaching the end position of the movable slide 27, both welding beams 31 move together and pull the film web 23 with it until both welding beams 31 lie on top of each other and hold the double film web 23 in place. The two superposed film webs 23 are then welded together by means of heat and pressure and subsequently separated by the separating wire down the centre of the weld seam. The block of material 3 is now completely enveloped by a piece of film web cut out of film web 23 and welded inside it and the cut film web 23 is welded to re-form a continuous film web 23.

[0048] A second embodiment of the invention will now be described with reference to FIGS. 8 and 9.

[0049]FIGS. 8 and 9 show from left to right a compression apparatus 110, a subsequent packaging apparatus 112 and another adjoining station on the right-hand side of FIGS. 8 and 9, which could be designated as a second packaging apparatus but will be called a wrapping unit 114 for the sake of differentiation.

[0050] The compression apparatus 110 has a slim, relatively tall frame with a rectangular base plate 116 and a total of four upwardly projecting pillars 118 at the four corners. A frame-fixed, pressure-resistant conveyor belt 120 is disposed between pillars 118 in the lower portion. This conveyor belt can be e.g. a slat conveyor made from hingingly connected aluminium slats. The conveyor device runs from left to right in FIGS. 8 and 9, i.e. from compression apparatus 110 to packaging apparatus 112.

[0051] The compression apparatus 110 also has a top conveyor belt 122 which essentially matches bottom conveyor belt 120, but can be moved vertically along the frame or, more precisely, along pillars 118 of the frame. For this purpose, guides 124, 126 are provided on pillars 118, and on both sides of the frame, i.e. in front of and behind the plane of the drawings in FIGS. 8 and 9, there are vertically disposed rotatable threaded spindles 128 which are accommodated by spindle nuts 130, which are fixed to the top conveyor belt 122.

[0052] Threaded spindles 128 are mounted in top and bottom connecting struts 132, 134, which each connect the top and bottom portions of side pillars 118 positioned behind each other in the direction of transport of conveyor belts 120, 122. Mounted on the top connecting strut 132 there is a connecting shaft 136 which runs transverse to the direction of transport, which can be driven by an electric motor 138 and also engages drivingly with the two threaded spindles 128 via angular gears which are not shown in detail. The rotation of the electric motor 138 therefore prompts a rotation of threaded spindles 128, which are synchronised via connecting shaft 136, therefore causing the top pressure-resistant conveyor belt 122 to lift up and down.

[0053] In the direction of transport, i.e. towards the right in FIGS. 8 and 9, the packaging apparatus 112 follows on from compression apparatus 110. The packaging apparatus also has a base plate 140 plus four pillars 142, 144, 146, 148 in the four corners of the rectangular base plate 140.

[0054] On the input side of packaging apparatus 112, i.e. to the left of FIGS. 8 and 9, there are feeder devices which permit the formation of a vertical film web curtain in front of the input side with the help of film webs fed in from the top and bottom. In detail, these feeder devices consist of top and bottom deflecting rollers 150, 152, 154, 156. The two film webs are pulled off from rolls of material 160, 162 not shown in FIG. 8, which, as can be seen in FIG. 9, are located to the side of packaging unit 112 and are deflected via the oblique deflecting rollers 150, 152.

[0055] Fixed to the frame of packaging apparatus 112, which is embodied here by the four pillars 142, 144, there is a bottom frame-fixed conveyor belt 164 which lies in the plane of the above-described belt conveyor 120 of the compression apparatus and can be driven in the same direction from left to right. Conveyor belt 164 may also be a slat conveyor made from e.g. aluminium slats. Whatever the case, it is designed to be pressure-resistant. Conveyor belt 164 works together with a top conveyor belt 166, which can be raised and lowered in relation to the bottom conveyor belt 164. For this purpose the top conveyor belt 166 is suspended with the help of threaded spindles 168, 170 from lateral top longitudinal spars 172, 174 of the frame of packaging apparatus 112.

[0056] The rotation of threaded spindles 168, 170 allows top conveyor belt 166 to be raised or lowered. Top conveyor belt 166 is adjusted so that the compaction and compression obtained in the compression apparatus 110 is maintained in packaging unit 112.

[0057] The compression apparatus 110 and the packaging apparatus 112 work as follows.

[0058] To start with, a stack of articles for packaging, e.g. non-woven materials for manufacturing nappies, feminine sanitary pads etc. is placed from the left in FIGS. 8 and 9 onto the bottom conveyor belt 120 of compression apparatus 110. Threaded spindles 128 are then rotated by electric motor 138 to lower the top conveyor belt 122 and the stack is compressed so that the air is removed from the stack and the packaging volume is decreased. The two conveyor belts 120, 122 are then set in motion so that the compressed stack is pushed from left to right to the input side of packaging apparatus 112. It comes into contact here with the vertical curtain formed by the top and bottom film webs which, in a previous step, have been welded approximately mid-height between the two conveyor belts to the left and right of the curtain.

[0059] The compressed stack transported towards the right in FIGS. 8 and 9 takes the curtain consisting of the two film webs with it towards the right into the space between the two conveyor belts 164, 166 of the packaging apparatus 112 and, in the process, is also pulled off from the two feeder rollers. Once the stack is completely in position between the two conveyor belts 164, 166, the film webs fed into from the top and bottom engage with top and bottom deflecting rollers 176, 178, which are vertically displaceable on guides 180. Guides 180 are located directly on the input side of the packaging apparatus on lateral vertical supports 182. Once the two film webs from the top and bottom rolls have been brought together at mid-height, they are welded together by a welding and cutting unit which is not shown in detail, and then separated so that, on the one hand, they are connected at the back of the exiting stack of material and, on the other hand, remain in contact as the said curtain. The next stack can now be pushed against the curtain.

[0060] According to this invention, the film web described so far consists of a relatively good quality material of e.g. 100_m thickness. Its function is to absorb the entire elastic recovery force of the stack due to compression. This film web need not necessarily stretch across the entire width of the stack. The function of the illustrated film web is not to cover the stack completely against dust, humidity and other contamination, but simply to absorb the elastic recovery force. The packaging of the material that is required for hygienic reasons takes place according to the invention at another station which, in this context, is located downstream of the packaging apparatus and will be designated as the wrapping apparatus 114.

[0061] The wrapping apparatus 114 is merely indicated diagrammatically. Its function is to wrap an inexpensive thinner film material around the stack crosswise to the direction of transport, perpendicular to the film web used in the packaging apparatus. This can be done in that the stack is rotated around an axis running parallel to the direction of transport, or in that a film web is wrapped around the stack in the manner of a satellite.

[0062] Wrapping devices of this type are disclosed in many embodiments and are not the subject of this invention. However, the invention does include the idea that a hygienically packaged, compressed, essentially square-shaped stack of rebounding material can be packaged in that to start with, a film web of expensive, strong material is wound around the stack and then a cheaper, thinner, less strong film material is wrapped around the stack in a direction offset by 90° so that a largely impenetrable hygienic closure is obtained.

[0063] Downstream of wrapping apparatus 114 there is an output table 184, from which the wrapped stacks can be removed by hand or using a fork-lift truck, or transferred to a conveyor which is not shown. 

1. A method for packaging a block consisting of a compressible material, in which a load is applied to the block of material (3) in one direction by a force designed to produce a compression, in which the block is wrapped in a film in this loaded state and is then released from said load once wrapped, characterized in that the block of material (3) to which the load is applied and a film web (23) tensioned parallel to the direction of force are brought together, thereby wrapping three of the circumferential surfaces of the block of material (3) with film web (23), the force required to generate the compression is replaced by a force acting in the same direction on the already wrapped surfaces of the block of material (3) to maintain a compression of the same order, and the film web (23) is pressed together, welded and separated at the fourth circumferential surface of the block of material (3).
 2. The method of claim 1, characterized in that the block of material (3) is pushed towards the tensioned film web (23).
 3. The method of claim 2, characterized in that the film web (23) is unwound from a roll of film (21).
 4. The method of claim 3, characterized in that the film web (23) is unwound from the roll of film (21), welded together and separated along the middle of the weld seam.
 5. The method of one of claims 1 to 4, characterized in that the block of material (3) is compressed by two pressure-resistant conveyor belts (120, 122) and, in the compressed state, is pushed by the latter towards the taut film web and between two pressure-resistant conveyor belts of the downstream packaging apparatus (112).
 6. The method of claim 5, characterized in that a welding and cutting device (176, 178) is provided which draws together the film webs fed in from the top and 10 bottom at mid-height behind the block of material positioned in packaging apparatus (112), welds them together and then separates them in such a way that the film webs remain connected both at the back of the block of material and inside the new curtain.
 7. The method of claims 5 or 6, characterized in that the block of material is first wrapped in one direction with a strong, good quality film which is chosen for its capacity to absorb the elastic recovery forces generated by the compression, and in that the block of material is then wrapped in a direction perpendicular to the first direction with an inexpensive thinner film that functions as a hygienic seal.
 8. A device for packaging a block consisting of a compressible material comprising a compression apparatus (1, 110) for producing a compressed block of material (3) and a packaging apparatus (2, 112) for packaging the block of material (3), characterized in that, the compression apparatus (1, 110) comprises a driveable compression unit (11) with means for gripping the block on opposite sides, in that the packaging apparatus (2, 112) has means for receiving the block of material (3) and for maintaining the compressed state of the block, in that between the compression apparatus and the packaging apparatus there is a film tensioning unit (18) for tensioning a film web parallel to the compression apparatus, and in that a film welding unit (19) is disposed between the film tensioning unit and the packaging apparatus (112).
 9. The device of claim 8, characterized in that the compression unit (11) has two bottom angled compression rails (14) and two top angled compression rails (15) and a clamping device which grasps angled compression rails (14, 15) for the purpose of sustaining a preferred position.
 10. The device of claim 9, characterized in that the compression unit (11) has a bottom fixed compression plate (12) and a top driveable compression plate (13), and the two angled compression rails (14, 15) are contrived so that they can be raised with respect to the bottom compression plate (12) to create free spaces (16, 17) in the clamped position.
 11. The device of claim 8, characterized in that the film tensioning unit (18) is fitted on the one hand with a roll of film (21) with a continuous film web (23) and, on the other hand, with a tensioning roller (22), with tensioning roller (22) being pre-tensioned so that under a horizontal load, it is pushed out of its vertical starting position and, when the horizontal load is removed, reverts to its starting position.
 12. The device of claim 8, characterized in that between the roll of film (21) and tensioning roller (22), two rollers for guiding and deflecting film web (23) are disposed at a distance from each other that is bigger than the block of material (3).
 13. The device of claim 9, characterized in that the two rollers for guiding and deflecting the film web are a bottom pair of rollers (24) and a top pair of rollers (25).
 14. The device of claim 5, characterized in that the film welding unit (19) has two welding beams (31) for connecting the free ends of film web (23), with at least one welding beam (31) being driveably contrived.
 15. The device of claim 11, characterized in that one welding beam (31) is additionally fitted with a separating wire which extends along the entire length of welding beam (31) and runs in the middle of welding beam (31), with the separating wire being disposed in such a plane to the heating surface of welding beam (31) that film web (23) is first welded and then separated inside the welded surface.
 16. The device of claim 8, characterized in that the receiver unit of the packaging apparatus (2) has at least one bottom remover gripper (28) and one top remover gripper (29), the position and dimensions of which are designed to coincide with the position and dimensions of the free spaces (16, 17) of compression unit (11), and which each have a film push rod (30) on the ends closest to compression unit (11).
 17. The device of claims 8 to 17, characterized in that the receiver unit of the packaging apparatus (2) is contrived as a movable unit (20) with a frame (26) and a movable slide (27), which can be displaced in relation to the fixed compression unit (11) of compression apparatus (1).
 18. The device of claim 8, characterized in that the means of the compression apparatus (110) for gripping the block of material from opposite sides are pressure-resistant conveyor belts (120, 122) which compress the compressed block as a result of being brought together, with the block then being transferred to the packaging apparatus (112) by driving the conveyor belts forward.
 19. The device of claim 8, characterized in that the means of the packaging apparatus (112) for gripping the block of material and sustaining the compressed state are pressure-resistant conveyor belts (164, 166) which can be driven in the direction of the exit of the packaging apparatus.
 20. The device of one of claims 18 or 19, characterized in that the conveyor belts (120, 122, 164, 166) of the compression apparatus (110) and/or the packaging apparatus (112) have slat plates consisting of rigid slats.
 21. The device of one of claims 18 to 20, characterized in that the means of the compression apparatus for compressing the block of material, and of the packaging apparatus (112) for sustaining the compressed state comprise bottom, frame-fixed and top, lowerable and stoppable conveyor belts (120, 122, 164, 166).
 22. The device of one of claims 18 to 21, characterized in that on the input side of packaging apparatus (112) there are top and bottom feeder devices (150, 152, 154, 156, 158, 160, 162) for film webs.
 23. The device of claim 22, characterized in that the feeder devices are deflecting rollers (150, 152, 154, 156, 158) which allow the film webs to be guided perpendicularly from above and below to in front of the input side of the packaging apparatus.
 24. The device of one of claims 18 to 23, characterized in that on the input side of packaging apparatus (112) there is a vertically displaceable welding and cutting device (176, 178).
 25. A packaged block of material consisting of compressible material, characterized in that the essentially square-shaped block of material is wrapped in a first direction with a strong plastic film selected for its capacity to absorb the elastic restoring forces of the compressed material, and in that the block of material is completely wrapped in a second direction perpendicular to the first direction with an appropriate light material as protection against dirt and moisture. 